Substitution and oxidative addition reactions of the monoolefin complex Rh(acac)(cyclooctene)(PCy3) including the X-ray structure analyses of Rh(acac)(PCy3)2 and [Rh(acac){(E)-CH=CHCy}(PCy3)2]BF4

Article abstract of DOI:10.1021/om9601458

The olefin complex Rh(acac)(cyclooctene)(PCy₃) (2), which is formed from Rh(acac)-(cyclooctene)₂ (1) and PCy₃ in nearly quantitative yield, reacts with CO and alkynes RC≡CR by ligand displacement to give Rh(acac)(CO)(PCy₃) (3) and Rh(acac)(η²-RC≡CR)(PCy₃) [R = CO₂Me (4), Ph (5)], respectively. The bis(phosphine) compound Rh(acac)(PCy₃)₂ (6) cannot be prepared directly from 2 and excess PCy₃ but via Rh(acac)(η²-HC≡CCO₂Me)(PCy₃) (7) as intermediate. The X-ray crystal structure analysis of 6 reveals that the rhodium is coordinated in a distorted square-planar manner with O-Rh-O and P-Rh-P bond angles of 85.9(1) and 105.63(4)°. Compound 2 reacts with H₂ in the presence of PCy₃ to yield Rh-(acac)H₂(PCy₃)₂ (8) and with HC≡CR/PCy₃ to give Rh(acac)H(C≡CR)(PCy₃)₂ [R = Ph (9), Cy (10), SiMe₃ (11)]. On treatment of 10 and 11 with HBF₄·OEt₂, the cationic alkenylrhodium(III) derivatives [Rh(acac){(E)-CH=CHCy}(PCy₃)₂]BF₄ (12) and [Rh(acac)(CH=CH₂)-(PCy₃)₂]BF₄ (13) are obtained. Labeling experiments using DBF₄·OEt₂ illustrate that the deuterium is found at the β-C carbon atom of the alkenyl ligand. Both 12 and [Rh(acac)-{(E)-CH=CDCy}(PCy₃)₂]BF₄ (12-d₁) react with NEt₃ to regenerate 10. The structure of 12 was determined by X-ray analysis. The coordination geometry around the metal center can be rationalized as a square pyramid with the alkenyl group in the apical position.

Full text of DOI:10.1021/om9601458

3436
Organometallics 1996, 15, 3436-3444
Su bstitu tion a n d Oxid a tive Ad d ition Rea ction s of th e
Mon oolefin Com p lex Rh (a ca c)(cycloocten e)(P Cy3)
In clu d in g th e X-r a y Str u ctu r e An a lyses of
Rh (a ca c)(P Cy3)2 a n d
[Rh (a ca c){(E)-CHdCHCy}(P Cy3)2]BF 4
Miguel A. Esteruelas,*,† Fernando J . Lahoz,† Enrique On˜ate,† Luis A. Oro,*,†
Laura Rodr´ıguez,† Paul Steinert,‡ and Helmut Werner*,‡
Departamento de Qu´ımica Inorga´nica, Instituto de Ciencia de Materiales de Arago´n,
Universidad de Zaragoza, CSIC, 50009 Zaragoza, Spain, and Institut fu¨r Anorganische
Chemie, Universita¨t Wu¨rzburg, Am Hubland, D-97074 Wu¨rzburg, Germany
Received February 28, 1996X
The olefin complex Rh(acac)(cyclooctene)(PCy3) (2), which is formed from Rh(acac)-
(cyclooctene)2 (1) and PCy3 in nearly quantitative yield, reacts with CO and alkynes RCtCR
by ligand displacement to give Rh(acac)(CO)(PCy3) (3) and Rh(acac)(η2-RCtCR)(PCy3) [R )
CO2Me (4), Ph (5)], respectively. The bis(phosphine) compound Rh(acac)(PCy3)2 (6) cannot
be prepared directly from 2 and excess PCy3 but via Rh(acac)(η2-HCtCCO2Me)(PCy3) (7) as
intermediate. The X-ray crystal structure analysis of 6 reveals that the rhodium is
coordinated in a distorted square-planar manner with O-Rh-O and P-Rh-P bond angles
of 85.9(1) and 105.63(4)°. Compound 2 reacts with H2 in the presence of PCy3 to yield Rh-
(acac)H2(PCy3)2 (8) and with HCtCR/PCy3 to give Rh(acac)H(CtCR)(PCy3)2 [R ) Ph (9),
Cy (10), SiMe3 (11)]. On treatment of 10 and 11 with HBF4‚OEt2, the cationic alkenylrhod-
ium(III) derivatives [Rh(acac){(E)-CHdCHCy}(PCy3)2]BF4 (12) and [Rh(acac)(CHdCH2)-
(PCy3)2]BF4 (13) are obtained. Labeling experiments using DBF4‚OEt2 illustrate that the
deuterium is found at the â-C carbon atom of the alkenyl ligand. Both 12 and [Rh(acac)-
{(E)-CHdCDCy}(PCy3)2]BF4 (12-d1) react with NEt3 to regenerate 10. The structure of 12
was determined by X-ray analysis. The coordination geometry around the metal center can
be rationalized as a square pyramid with the alkenyl group in the apical position.
In tr od u ction
As a continuation of this work, we became interested
to find out whether the rhodium complex Rh(acac)-
(cyclooctene)(PCy3) behaves similarly to its iridium
counterpart and whether it can also be used as starting
material for the preparation of the more nucleophilic
bis(phosphine)metal derivative Rh(acac)(PCy3)2. One of
us has recently shown that the acetato compound Rh-
(η2-O2CMe)(PiPr3)2 which is monomeric3 and thus prob-
ably structurally related to the desired acetylacetonato
species Rh(acac)(PCy3)2 is an excellent precursor both
for the preparation of alkyne and vinylidenerhodium
complexes4 and also for the stepwise trimerization of a
terminal alkyne; the latter reaction does not lead to a
benzene but selectively to a hexadienyne derivative.5
In this paper we report on the synthesis of Rh(acac)-
(cyclooctene)(PCy3) and Rh(acac)(PCy3)2, as well as on
substitution and oxidative addition reactions of the
monoolefin complex. In addition, we illustrate the
completely different behavior of the bis(phosphine)
complex Rh(acac)(PCy3)2 when compared with the car-
boxylato derivatives Rh(η2-O2CR)(PiPr3)2 (R ) CH3, CF3)
toward molecular hydrogen and terminal alkynes which
is probably due to the rigidity of the Rh(acac) ring
system.
In the search for transition-metal complexes which
are catalytically active in the hydrogenation, hydrosi-
lylation, and hydrostannylation of unsaturated organic
substrates, we have recently reported on the reactivity
of the (acetylacetonato)iridium compound Ir(acac)(cy-
clooctene)(PCy3),1 which is formed by ligand displace-
ment from Ir(acac)(cyclooctene)2 and PCy3.2 The cy-
clooctene compound Ir(acac)(cyclooctene)(PCy3) not only
reacts with silanes HSiR3 to give Ir(acac)H(SiR3)(PCy3)
and with HSnPh3 to afford Ir(acac)H(SnPh3)(PCy3) but
in the presence of 3 equiv of phenylacetylene also to
yield an unusual chelated alkynyl(alkenyl)iridium(III)
complex which is a result of the oxidative addition of
the HCt bond of an alkyne, the insertion of a second
alkyne into an Ir-C3(acac) bond, and the subsequent
insertion of a third alkyne into the Ir-H bond initially
formed.1 Moreover, the five-coordinate hydrido-silyl
derivative Ir(acac)H(SiEt3)(PCy3) not only adds one
molecule of hydrogen to give the trihydrido compound
Ir(acac)H3(SiEt3)(PCy3) but is also an active catalyst for
the addition of HSiR3 to phenylacetylene.1
† Universidad de Zaragoza.
(3) Werner, H.; Scha¨fer, M.; Nu¨rnberg, O.; Wolf, J . Chem. Ber. 1994,
127, 27.
(4) Scha¨fer, M.; Wolf, J .; Werner, H. J . Organomet. Chem. 1995,
485, 85.
(5) Werner, H.; Scha¨fer, M.; Wolf, J .; Peters, K.; von Schnering, H.
G. Angew. Chem. 1995, 107, 213; Angew. Chem., Int. Ed. Engl. 1995,
34, 191.
‡ Universita¨t Wu¨rzburg.
X Abstract published in Advance ACS Abstracts, J une 15, 1996.
(1) Esteruelas, M. A.; Lahoz, F. J .; On˜ate, E.; Oro, L. A.; Rodr´ıguez,
L.; Organometallics 1996, 15, 823.
(2) Esteruelas, M. A.; Lahoz, F. J .; On˜ate, E.; Oro, L. A.; Rodr´ıguez,
L.; Organometallics 1995, 14, 263.
S0276-7333(96)00145-8 CCC: $12.00 © 1996 American Chemical Society
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Reactions of a Monoolefin Complex
Organometallics, Vol. 15, No. 15, 1996 3437
Sch em e 1
Sch em e 2
room temperature, the spectrum of 4 does not contain
resonances due to the methyl and carbonyl carbon atoms
of the acetylacetonato ligand. They were located at
188.9, 183.1 (CO) and 28.35 and 26.65 (CH3) ppm in the
spectrum at -50 °C. The spectrum of 5 at room
temperature displays two broad resonances due to the
carbonyl groups at 187.7 and 183.4 ppm, which are
converted into singlets at -50 °C. At this temperature,
the spectrum also contains a doublet at 28.15 (J P-C ) 4
Hz) and a singlet at 26.95 ppm, assigned to the in-
equivalent methyl groups. At -50 °C, the spectra of
both compounds show only one resonance at 88.55 (4)
and 86.2 (5) for the acetylenic carbon atoms, suggesting
that in both compounds the CtC bond lies perpendicu-
lar to the coordination plane of the rhodium as should
be expected according to the Dewar-Chatt-Duncanson
bonding scheme.
Resu lts a n d Discu ssion
1. Syn th esis a n d Ch a r a cter iza tion of Rh (a ca c)-
(cycloocten e)(P Cy3) an d Rh (acac)(P Cy3)2. On treat-
ment with PCy3, the bis(cyclooctene)rhodium complex
1 (Scheme 1) affords the phosphine derivative Rh(acac)-
(cyclooctene)(PCy3) (2) in 95% yield. The reaction
proceeds at room temperature and does not lead to
displacement of the second olefin even if excess phos-
phine is used. The complex 2, which is a yellow solid,
is relative stable under argon at -20 °C. The cy-
clooctene ligand of 2 is easily displaced by strong
π-acceptor ligands such as carbon monoxide, acetylene-
dicarboxylic dimethyl ester and diphenylacetylene. By
passage of a slow stream of carbon monoxide through a
toluene solution of 2, the carbonyl complex Rh(acac)-
(CO)(PCy3) (3) is formed. Similarly, treatment of hex-
ane solutions of 2 with the stoichiometric amount of
acetylenedicarboxylic dimethyl ester and diphenylacety-
lene affords Rh(acac)(η2-RCtCR)(PCy3) [R ) CO2Me (4),
Ph (5)] as orange (4) or yellow (5) solids in good yield
[89% (4), 86% (5)].
The above mentioned spectroscopic data indicate that
complexes 4 and 5 have a rigid structure only at low
temperature. At room temperature, a slow (on the NMR
time scale) exchange process takes place, which involves
the relative positions of the alkyne and phosphine
ligands (eq 1).
The IR spectra of 2-5 in Nujol display two strong ν-
(CO) absorptions between 1590 and 1500 cm-1 indicat-
ing that the acetylacetonato ligand is coordinated in a
η2-oxygen bonding mode.6 The π-coordination of the
alkyne in 4 and 5 is also supported by the IR spectra of
these compounds, in which the CtC stretching fre-
quency is found at 1890 (4) and 1910 (5) cm-1, thus
shifted 260 (4) and 310 (5) cm-1 to lower wavenumbers
if compared with the free alkyne. In agreement with
the square-planar coordination of the rhodium atom, at
room temperature the 1H NMR spectra of 2 and 3
display two singlets between 1.91 and 1.61 ppm for the
protons of the methyl groups of the acetylacetonato
ligand. These spectra are temperature invariant down
Complex 2 does not react with an excess of tricyclo-
hexylphosphine. However, the addition of 1 equiv of
methyl propiolate to equimolar amounts of 2 and
tricyclohexylphosphine in toluene leads to the formation
of the bis(phosphine) derivative Rh(acac)(PCy3)2 (6). The
reaction proceeds via the intermediate Rh(acac)(η2-
HCtCCO2Me)(PCy3) (7). In fact, the addition of the
stoichiometric amount of methyl propiolate to a solution
of 2 in hexane affords 7, which subsequently yields 6
upon the addition of 1 equiv of tricyclohexylphosphine
(Scheme 2).
Complex 6 was characterized by elemental analysis,
1
to -50 °C. However, the H NMR spectra of 4 and 5
1
IR and H and 31P{1H} NMR spectroscopy, and single-
are temperature dependent. At room temperature, the
methyl protons of the acetylacetonato ligands give only
one singlet at 1.86 (4) and 1.94 (5) ppm, while at -50
°C they display two singlets at 1.91 and 1.80 (4) and
2.01 and 1.86 (5) ppm, respectively. The 13C{1H} NMR
spectra of 4 and 5 are also temperature dependent. At
crystal X-ray diffraction studies. A view of the molec-
ular geometry is shown in Figure 1, and selected bond
distances and angles are listed in Table 1. The coordi-
nation geometry around the rhodium center is almost
square-planar. The deviations from the best plane are
-0.0030(5) (Rh), -0.005(1) (P(1)), 0.016(1) (P(2)), 0.127-
(3) (O(1)), and -0.064(3) (O(2)) Å. The most noticeable
structural feature is the P-Rh-P angle (105.63(4)°),
(6) Oro, L. A.; Carmona, D.; Esteruelas, M. A.; Foces-Foces, C.; Cano,
F. H. J . Organomet. Chem. 1986, 307, 83.
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3438 Organometallics, Vol. 15, No. 15, 1996
Esteruelas et al.
Sch em e 3
F igu r e 1. Molecular diagram of complex Rh(acac)(PCy3)2
(6).
methyl protons of the acetylacetonato ligand, while at
-50 °C two singlets at 1.88 and 1.75 ppm are observed,
in agreement with the square-planar structure proposed
in Scheme 2. In addition, a doublet at 5.63 ppm with a
Rh-H coupling constant of 3 Hz is assigned to the tCH
proton. The temperature behavior of the 13C{1H} NMR
spectrum of 7 is similar to that of 5. At room temper-
ature, the spectrum shows two broad resonances cen-
tered at 188.5 and 182.8 ppm and a singlet at 27.15
ppm, which are assigned to the carbonyl and methyl
carbons of the acetylacetonato ligand. At -50 °C, the
broad resonances are converted into singlets, while the
singlet at 27.15 ppm is split into a singlet at 27.9 ppm
and a doublet at 26.9 ppm with a P-C coupling constant
of 5 Hz. At room temperature, the signals of the
acetylenic carbon atoms of the π-alkyne ligand appear
at 93.8 and 76.0 ppm as doublet-of-doublets with Rh-C
coupling constants of 17 and 19 Hz and a P-C coupling
constant of 5 Hz. At -50 °C, these carbon atoms display
broad resonances at 95.5 and 76.9 ppm.
2. Oxid a tive Ad d ition Rea ction s of Com p lex 2.
While complex 6 does not react with tricyclohexylphos-
phine or molecular hydrogen individually, the dihydrido
compound Rh(acac)H2(PCy3)2 (8) is easily formed by
passing a slow stream of molecular hydrogen through
a toluene solution of 2 in the presence of a stoichiometric
amount of tricyclohexylphosphine. Similarly, the ad-
dition of 1 equiv of phenylacetylene, cyclohexylacetylene,
or (trimethylsilyl)acetylene to equimolecular amounts
of 2 and tricyclohexylphosphine in solution leads to the
hydrido-alkynyl complexes Rh(acac)H(C2R)(PCy3)2 [R
) Ph (9), Cy (10), SiMe3 (11); see Scheme 3]. The
behavior of 6 toward molecular hydrogen and terminal
alkynes is in contrast with that previously observed for
Rh(η2-O2CR)(PiPr3)2, which on treatment with molecular
hydrogen and terminal alkynes affords Rh(η2-O2CR)-
H2(PiPr3)2 and Rh(η2-O2CR)H(C2R′)(PiPr3)2 (R ) CH3,
CF3), respectively.4
Ta ble 1. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for th e Com p lex Rh (a ca c)(P Cy3)2 (6)
Rh-P(1)
Rh-P(2)
Rh-O(1)
Rh-O(2)
O(1)-C(2)
2.252(1)
2.260(1)
2.089(4)
2.083(3)
1.276(6)
C(1)-C(2)
C(2)-C(3)
C(3)-C(4)
O(2)-C(4)
C(4)-C(5)
1.503(9)
1.387(6)
1.389(8)
1.279(6)
1.508(7)
P(1)-Rh-P(2)
P(1)-Rh-O(1)
P(1)-Rh-O(2)
P(2)-Rh-O(1)
P(2)-Rh-O(2)
O(1)-Rh-O(2)
Rh-O(1)-C(2)
105.63(4)
84.34(8)
169.98(9)
169.26(9)
84.26(9)
85.9(2)
O(1)-C(2)-C(1)
O(1)-C(2)-C(3)
C(1)-C(2)-C(3)
C(2)-C(3)-C(4)
C(3)-C(4)-C(5)
O(2)-C(4)-C(3)
O(2)-C(4)-C(5)
115.1(4)
125.7(4)
119.3(4)
125.5(4)
120.0(4)
125.7(5)
114.3(5)
128.4(3)
which is statistically identical with the P-Rh-P angle
of the related complex Rh(η2-O2CCH3)(PiPr3)2 (106.00-
(4)°).3 These relatively large values can be explained
by the fact that for both compounds the two phosphine
ligands, cis disposed, experience a large steric hin-
drance, as a result of the large cone angle of the
tricyclohexylphosphine and triisopropylphosphine groups.
The â-diketonato bite angle O-Rh-O of 85.9(1)° is
similar to values found in related chelated rhodium
complexes.7 The Rh-P, Rh-O, C-O, and C-C dis-
tances are clearly in the range expected and deserve no
further comment.
In agreement with the structure shown in Figure 1,
1
the H NMR spectrum of 6 contains only one singlet at
1.81 ppm for the protons of the methyl groups of the
â-diketonate ligand, while the 31P{1H} NMR spectrum
shows a doublet at 49.9 ppm with a Rh-P coupling
constant of 191 Hz.
Complex 7 was isolated as a yellow solid in 68% yield.
In the IR spectrum in Nujol the most noticeable absorp-
tion is that of the CtC bond stretch, which appears at
1810 cm-1, i.e., shifted by 311 cm-1 when compared with
1
the free alkyne (2121 cm-1). Similarly to the H NMR
Recently, we have reported on the synthesis of the
iridium(III) complexes Ir(acac)H2(PCy3)2 and Ir(acac)H-
(C2R)(PCy3)2 (R ) Ph, Cy, SiMe3), which were obtained
on reaction of Ir(acac)(cyclooctene)(PCy3) with HX (X )
H, C2R) in the presence of an excess of phosphine.
These reactions probably occur by the oxidative addition
of HX to the bis(phosphine) intermediate Ir(C3-acac)-
(cyclooctene)(PCy3)2, which is formed by reaction of Ir-
spectra of 4 and 5, the 1H NMR spectrum of 7 is
temperature dependent. At room temperature, the
spectrum shows only one singlet at 1.80 ppm for the
(7) (a) Leipoldt, J . G.; Lamprecht, G. J .; Van Zyl, G. J . Inorg. Chim.
Acta 1985, 96, L31. (b) Van Zyl, G. J .; Lamprecht, G. J .; Leipoldt, J .
G. Inorg. Chim. Acta 1985, 102, L1. (c) Duan, Z.; Hampden-Smith, M.
J .; Duesler, E. N.; Rheingold, A. L. Polyhedron 1994, 13, 609.
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Reactions of a Monoolefin Complex
Organometallics, Vol. 15, No. 15, 1996 3439
(acac)(cyclooctene)(PCy3) with phosphine.1 A similar
reaction pathway for the formation of 8-11 does not
seem likely, given that the bis(phosphine) complex 6
does not undergo oxidative addition reactions, most
probably as a result of the steric hindrance imposed by
the tricyclohexylphosphine groups and of the stability
of the Rh(acac) chelate ring system. In this context, it
should be mentioned that the η2-O2(acac) f η1-C3(acac)
conversion is known for iridium(I),6 whereas it has no
precedent for rhodium(I). Hence, it can be proposed that
in the presence of the HX substrates 2 is in equilibrium
with undetectable concentrations of the five-coordinate
Rh(acac)H(X)(PCy3) species, and thus the addition of
phosphine could shift the equilibrium toward the rhod-
ium(III) complexes by coordination, generating in this
way 8-11. The stability of the Rh(acac) ring system
also seems to be responsible for the different behavior
of 6 when compared with that of the carboxylato
complexes Rh(η2-O2CR)(PiPr3)2 (R ) CH3, CF3).
The formation of the five-coordinate rhodium(III)
intermediates Rh(acac)H(C2R)(PCy3) most probably
involves the generation of labile species related to 7,
Rh(acac)(η2-HCtCR)(PCy3), which evolve by carbon-
hydrogen activation of the H-C(sp) bond of the π-alkyne
ligands. The high stability of 7 toward the C-H
activation of the H-C(sp) bond of the coordinated
methyl propiolate is not surprising. We note in this
context that the complexes Rh{η1-OC(O)CF3}(η2-
HCtCR)(PiPr3)2 (R ) H, Ph) afford the corresponding
six-coordinate hydrido-alkynyl RhH(η2-O2CCF3)(C2R)-
(PiPr3)2 derivatives in benzene at room temperature,
whereas the compound Rh{η1-OC(O)CF3}(η2-HCtCCO2-
Me)(PiPr3)2 is stable under the same conditions.4
F igu r e 2. Molecular diagram of complex [Rh(acac){(E)-
CHdCHCy}(PCy3)2]BF4 (12).
Sch em e 4
Complex 8 was isolated as a white, air-stable solid in
67% yield. In agreement with the cis disposition of the
hydrido ligands, the IR spectrum in Nujol displays two
strong absorptions at 2120 and 2085 cm-1 assigned to
The presence of only one hydrido ligand in these
compounds was inferred from the 31P{1H} NMR spectra
which contain doublets between 38 and 35 ppm (J Rh-P
= 103 Hz), in agreement with the mutually trans
disposition of the phosphine ligands. Under off-reso-
nance conditions these signals split into doublets-of-
doublets due to P-H coupling.
1
the Ir-H stretches, while in the H NMR spectrum the
hydride resonance appears at -22.18 ppm as a doublet-
of-triplets with Rh-H and P-H coupling constants of
20 and 16 Hz, respectively. The 31P{1H} NMR spectrum
contains a doublet at 15.8 ppm with a Rh-P coupling
constant of 117 Hz, indicating that the phosphine
ligands are equivalent and mutually trans disposed.
Under off-resonance conditions the doublet is split into
a doublet-of-triplets due to P-H coupling.
P r oton a tion of 10 a n d 11. Treatment of complex
10 with a stoichiometric amount of HBF4‚OEt2 in
diethyl ether leads to the precipitation of a yellow solid,
which was characterized as the five-coordinate alkenyl
complex [Rh(acac){(E)-CHdCHCy}(PCy3)2]BF4 (12,
Complexes 9-11 were isolated as white or pale yellow
solids by addition of methanol. Although the reactions
shown in Scheme 2 spectroscopically proceed nearly
quantitatively, the products were obtained in 45-50%
yield as a result of their moderate solubility in the
alcohol. The most noticeable features in the IR spectra
of 9-11 (in Nujol) are the two bands between 2155 and
2042 cm-1, which were assigned to the ν(Ir-H) and ν-
(CtC) vibrations. The presence of an alkynyl ligand
in these compounds is also supported by the 13C{1H}
NMR spectra. The signal of the R-C carbon atom
appears at about 103 ppm as doublet-of-triplets with
Rh-C and P-C coupling constants between 48 and 40
Hz and 18 and 16 Hz, respectively, while the â-C carbon
atom gives rise to a doublet at about 107 ppm with a
Rh-C coupling constant of 10 Hz. In the 1H NMR
spectra, the hydrido ligands display doublet-of-triplets
between -19.33 and -18.79 ppm with Rh-H and P-H
coupling constants of about 18 and 13 Hz, respectively.
1
Scheme 4) by elemental analysis, IR and H, 31P{1H},
and 13C{1H} NMR spectroscopy, and an X-ray diffraction
study. The molecular structure is presented in Figure
2, while selected bond distances and angles are listed
in Table 2. The most remarkable features of the
structure are the square-pyramidal coordination of the
metal with the alkenyl group located at the apex and
the trans position of the two substituents C6H11 and Rh-
(acac)(PCy3)2 at the CdC double bond. The four atoms
O(1), O(2), P(1), and P(2) forming the base of the
pyramid are approximately in one plane, while the
rhodium atom is located 0.1384(8) Å above this plane
toward the apical position. As a result of the large steric
hindrance experienced by the two cis disposed phos-
phine ligands, the P-Rh-P angle (105.3(1)°) strongly
deviates from the ideal value of 90°. The acetylaceto-
nato bite angle O-Rh-O (87.3(2)°) is similar to that
found in 6.
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3440 Organometallics, Vol. 15, No. 15, 1996
Esteruelas et al.
from the R-C to the â-C carbon atom.14 Thus, at first
glance, complex 10 has three nucleophilic centers,
namely the metal, the hydrido ligand, and the â-C
carbon atom of the alkynyl group. Therefore, the initial
electrophilic attack of the proton, which subsequently
affords the alkenyl derivative 12, could occur by the
reaction pathways shown in Scheme 5. According to
pathway a , the protonation takes place at the metal
center to yield a dihydrido-alkynyl intermediate, which
could afford a hydrido-π-alkyne species by intramo-
lecular reductive elimination. The subsequent insertion
of the π-alkyne ligand into the Rh-H bond should lead
to 12. According to pathway b, the initial formation of
an alkynyl dihydrogen intermediate is followed by the
electrophilic attack of the acidic proton of the dihydro-
gen ligand at the â-C carbon atom of the alkynyl group.
Migratory insertion of the resulting vinylidene group
into the Rh-H bond could also give 12. A similar
mechanism has been proposed for the formation of Os-
{(E)-CHdCHCy}Cl(CO)(PiPr3)2 from OsHCl(CO)(PiPr3)2
and cyclohexylacetylene.16 Pathway c suggests that the
protonation directly occurs at the â-C carbon atom of
the alkynyl group.17 As discussed for route b, the
subsequent migratory insertion of the vinylidene ligand
into the metal-hydride bond would lead to 12.
If the reaction of 10 with HBF4 to give 12 goes via
pathway a or b, treatment of 10 with DBF4 should
result in an approximate 1:1 distribution of the deute-
rium at the R-C and â-C carbon atoms of the alkenyl
ligand. However, the addition of a stoichiometric amount
of DBF4 to a suspension of 10 in diethyl ether leads
almost exclusively to 12-d1 with the deuterium atom
located on the â-C carbon atom of the alkenyl ligand.
This has been confirmed by the 2H NMR spectrum
which shows only one resonance at 4.33 ppm. According
to this observation there is no doubt that the reaction
of 10 with HBF4 occurs along pathway c. The reaction
is reversible, and thus, on treatment of 12-d1 with a
stoichiometric amount of triethylamine, complex 10 is
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for th e Ca tion of Com p lex
[Rh (a ca c){(E)-CHdCHCy}(P Cy3)2]BF 4 (12)
Rh-P(1)
Rh-P(2)
Rh-O(1)
Rh-O(2)
Rh-C(1)
C(1)-C(2)
C(2)-C(3)
2.336(3)
2.357(3)
2.049(8)
2.054(7)
1.98(1)
O(1)-C(9)
1.27(1)
1.49(2)
1.39(2)
1.37(2)
1.27(1)
1.49(2)
C(9)-C(10)
C(9)-C(11)
C(11)-C(12)
O(2)-C(12)
C(12)-C(13)
1.29(2)
1.54(2)
P(1)-Rh-P(2)
P(1)-Rh-O(1)
P(1)-Rh-O(2)
P(1)-Rh-C(1)
P(2)-Rh-O(1)
P(2)-Rh-O(2)
P(2)-Rh-C(1)
O(1)-Rh-O(2)
O(1)-Rh-C(1)
O(2)-Rh-C(1)
105.3(1)
84.4(3)
168.6(2)
92.2(2)
168.4(3)
82.1(2)
93.7(3)
87.3(2)
92.3(5)
96.0(4)
Rh-C(1)-C(2)
124.2(9)
121(1)
127.5(7)
116(1)
126(1)
118(1)
124(1)
119(1)
127(1)
114(1)
C(1)-C(2)-C(3)
Rh-O(1)-C(9)
O(1)-C(9)-C(10)
O(1)-C(9)-C(11)
C(10)-C(9)-C(11)
C(9)-C(11)-C(12)
C(11)-C(12)-C(13)
O(2)-C(12)-C(11)
O(2)-C(12)-C(13)
The Rh-C(1) distance (1.98(1) Å) is shorter than the
Rh-C distances found in related six-coordinate alkenyl-
rhodium(III) compounds such as Rh(η5-C5Me5)(2,6-C6H3-
Me2){(E)-C(CO2Me)dCHCO2Me}(PMe3) (2.065(3) Å),
Rh(η5-C5Me5)(2,6-C6H3Me2){(Z)-C(CO2Me)dCHCO2Me}-
(PMe3) (2.056(3) Å),8 Rh(CPhdCPhCPhdCHCH2)(acac)-
(PMe3)2 (2.032(4) Å),9 Rh(η5-C5H5){(E)-CPhdCHPh}{η1-
OC(O)CF3}(PiPr3) (2.189(13) Å), and Rh(η5-C5H5)-
{CPhdCH(C6H4)}{η1-OC(O)CF3}(PiPr3) (2.066(7) Å)10
and statistically identical with those reported for the
complexes Rh{C(CHdCHCO2Me)dCHCO2Me}(CtCCO2-
Me)(η2-O2CCH3}(PiPr3)2 (2.015(9) Å)5 and Rh{C(CF3)d
C(CF3)CH2CH2}(acac)(py)2 (2.020(7) Å).11 The C(1)-
C(2) bond length (1.29(2) Å) is similar to that found in
the above-mentioned compounds, and it agrees well with
average carbon-carbon bond distances for a C(sp2)-
C(sp2) double bond (1.32(1) Å).12
In agreement with the structure shown in Figure 2,
the IR spectrum of 12 in Nujol shows two strong ν(CO)
absorptions at 1570 and 1530 cm-1, due to the carbonyl
1
groups of the â-diketonato ligand. The H NMR spec-
trum, which is not temperature dependent, contains
only one singlet for the methyl protons of the acac unit
at 2.11 ppm, while the vinylic protons of the alkenyl
ligand are located at 6.50 (RhCHd) and 4.25 (dCHCy)
ppm. In agreement with the E-stereochemistry, the
H-H coupling constant is 10 Hz.13 In the 13C{1H} NMR
spectrum, the most noticeable resonances are those
corresponding to the C(sp2) carbon atoms of the unsat-
urated η1-carbon ligand. The resonance of the R-C
carbon atom is observed at 111.6 ppm as a doublet-of-
triplets with Rh-C and P-C coupling constants of 35
and 9 Hz, respectively, while the resonance of the â-C
carbon atom appears at 135.6 ppm as a singlet. The
31P{1H} NMR spectrum shows a doublet at 28.7 ppm
with a Rh-P coupling constant of 132 Hz.
regenerated. The conclusion is that the pKa of the
+
alkenyl ligand is lower than the pKa of HNEt3
.
Under the same experimental conditions as those
previously described for the preparation of 12, the
hydrido-alkynyl complex 11 affords [Rh(acac)(CHdCH2)-
(PCy3)2]BF4 (13, Scheme 4). There are precedents for
the cleavage of the Si-C bond in related processes. The
protonation of the alkynyl complex Rh2(µ-OOCCH3)(µ-
η1:η2-C2SiMe3)(CO)2(PCy3)2 with HBF4‚OEt2 leads to the
vinylidene-bridged rhodium compound [Rh2(µ-OOCCH3)-
(µ-CdCH2)(CO)2(PCy3)2]BF4.18 The vinylidene ligand
CdCH2 of the complex [OsI(η6-C6H6)(CdCH2)(PMetBu2)]-
PF6 is formed on treatment of OsI2(η6-C6H6)(PMetBu2)
with AgPF6 in the presence of (trimethylsilyl)acety-
lene.19 With the same alkyne, the iridium complex
In general the coordination of an acetylide anion to a
transition metal center transfers the nucleophilicity
(14) Elschenbroich, Ch.; Salzer, A. Organometallics; VCH
Verlagsgesellschaft: Weinheim, Germany, 1989.
(8) J ones, W. D.; Chandler, V. L.; Feher, F. J . Organometallics 1990,
9, 164.
(9) Egan, J . W.; Hughes, R. P.; Rheingold, A. L. Organometallics
1987, 6, 1578.
(15) The protonation of saturated transition metal hydrido com-
pounds has been described as an useful synthetic method for the
preparation of dihydrogen compounds. See: J essop, P. G.; Morris, R.
H. Coord. Chem. Rev. 1992, 121, 155.
(10) Werner, H.; Wolf, J .; Schubert, U.; Ackermann, K. J . Orga-
nomet. Chem. 1986, 317, 327.
(11) Dean, C. E.; Kemmitt, R. D. W.; Russell, D. R.; Schilling, M. D.
J . Organomet. Chem. 1980, 187, C1
(12) Orpen, A. G.; Brammer, L.; Allen, F. H.; Kennard, O.; Taylor,
R. J . Chem. Soc., Dalton Trans. 1989, S1.
(13) Werner, H.; Esteruelas, M. A.; Otto, H. Organometallics 1986,
5, 2295.
(16) Esteruelas, M. A.; Oro, L. A.; Valero, C. Organometallics 1995,
14, 3596.
(17) The addition of electrophiles to alkynylmetal complexes is a
general method of preparing vinylidene compounds. See: Bruce, M. I.
Chem. Rev. 1991, 91, 197.
(18) Esteruelas, M. A.; Lahoz, F. J .; On˜ate, E.; Oro, L. A.; Rodr´ıguez,
L.; Organometallics 1993, 12, 4219.
(19) Knaup, W.; Werner, H. J . Organomet. Chem. 1991, 411, 471.
+
+

Reactions of a Monoolefin Complex
Organometallics, Vol. 15, No. 15, 1996 3441
Sch em e 5
trans-IrCl(CdCH2)(PiPr3)2 has been prepared.20 It has
been suggested that these desilylation processes are due
to the presence of traces of water in the reaction media
acting as an electrophilic reagent.19,21 We note that, in
contrast to compounds containing silylvinylidene ligands,
corresponding species with silylalkynyl ligands are quite
stable in aqueous media. This is exemplified, i.e., by
the preparation of the complex Rh(CtCSiMe3)(PMe3)3
from cis-[RhH(CtCSiMe3)(PMe3)3]Cl in concentrated
aqueous KOH.22 Therefore, the formation of 13 from
the silylalkynyl-hydrido complex 11 is in full agree-
ment with the participation of vinylidenerhodium spe-
cies (pathway c, Scheme 5) as reaction intermediates.
With regard to the structural proposal for complex
13 we note that the IR spectrum in Nujol shows two
ν(CO) absorptions at 1573 and 1530 cm-1. The 1H NMR
spectrum contains only one singlet for the methyl
protons of the â-diketonato ligand at 2.11 ppm, while
the signals of the vinyl protons appear at 7.31 (RhCHd),
4.38 and 4.22 (dCH2) ppm. In the 13C{1H} NMR
spectrum, the resonance of the R-C carbon atom is
observed at 127.3 ppm as a doublet-of-triplets with
Rh-C and P-C coupling constants of 37 and 9 Hz,
respectively; the resonance of the â-C carbon atom
appears at 117.6 as a singlet. In accordance with the
square-pyramidal geometry, proposed in Scheme 4, the
31P{1H} NMR spectrum of 13 displays a doublet at 28.7
ppm with a Rh-P coupling constant of 130 Hz.
presence of methyl propiolate. The reaction involves the
displacement of the cyclooctene ligand by the terminal
alkyne to give Rh(acac)(η2-HCtCCO2Me)(PCy3) and the
subsequent sustitution of the π-alkyne by the phos-
phine.
The X-ray structural characterization of Rh(acac)-
(PCy3)2 proves the presence of a large P-Rh-P angle
(105.63(4)°), probably as a result of the steric hindrance
between the two cis disposed phosphine ligands. The
bis(phosphine) complex does not react with molecular
hydrogen and terminal alkynes by oxidative addition.
However, the rhodium(III) compounds Rh(acac)H(X)-
(PCy3)2 (X ) H, CtCPh, CtCCy, CtCSiMe3) can be
obtained by addition of HX to Rh(acac)(cyclooctene)-
(PCy3) in the presence of the stoichiometric amount of
tricyclohexylphosphine. The protonation of the rhod-
ium(III) hydrido-alkynyl derivatives with HBF4‚OEt2
affords the cationic five-coordinate alkenyl complexes
[Rh(acac){(E)-CHdCHR}(PCy3)2]BF4 (R ) Cy, H). These
reactions proceed via the initial electrophilic attack of
the proton at the â-C carbon atom of the alkynyl ligand.
As shown by the X-ray crystal structure analysis of 12,
the coordination geometry around the rhodium atom of
these alkenyl compounds can be described as square-
pyramidal with the alkenyl group in the apical position.
In conclusion, the monoolefin complex Rh(acac)(cy-
clooctene)(PCy3) is a useful starting material for the
preparation of new organometallic rhodium compounds,
including π-alkyne, hydrido-alkynyl, and cationic five-
coordinate alkenylmetal derivatives.
Con clu d in g Rem a r k s
The results of this study have revealed that the
olefinic unit of Rh(acac)(cyclooctene)(PCy3) can be easily
displaced by strong π-acceptor ligands such as carbon
monoxide, acetylenedicarboxylic dimethyl ester, and
diphenylacetylene. The bis(phosphine) complex Rh-
(acac)(PCy3)2 is not accessible by direct reaction of Rh-
(acac)(cyclooctene)(PCy3) and tricyclohexylphosphine.
However, it can be prepared from 2 and PCy3 in the
Exp er im en ta l Section
Gen er a l Con sid er a tion s. All reactions were carried out
under an argon atmosphere using Schlenk tube techniques.
Solvents were dried and purified by known procedures and
distilled under argon prior to use. The starting complex Rh-
(acac)(cyclooctene)2 (1) was prepared by a published method.23
Elemental analyses were performed with a Perkin-Elmer 240
XL microanalyzer. NMR spectra were recorded on Varian 200
XL or Varian UNITY 300 instruments. Chemical shifts are
expressed in parts per million, downfield from Si(CH3)4
(13C{1H}, 1H) and 85% H3PO4 (31P{1H}). Infrared spectra were
obtained from a Perkin-Elmer 783 instrument.
(20) (a) Ho¨hn, A.; Otto, H.; Dziallas, M.; Werner, H. J . Chem. Soc.,
Chem. Commun. 1987, 852. (b) Ho¨hn, A.; Werner, H. J . Organomet.
Chem. 1990, 382, 255.
(21) Espuelas, J .; Esteruelas, M. A.; Lahoz, F. J .; Oro, L. A.; Ruiz,
N. J . Am. Chem. Soc. 1993, 115, 4683.
(22) Zargarian, D.; Chow, P.; Taylor, N. J .; Marder, T. B. J . Chem.
Soc., Chem. Commun. 1989, 540.
(23) Diversi, P.; Ingrosso, G.; Immirzi, A.; Zocchi, M. J . Organomet.
Chem. 1977, 125, 253.
+
+

3442 Organometallics, Vol. 15, No. 15, 1996
Esteruelas et al.
P r ep a r a tion of Rh (a ca c)(cycloocten e)(P Cy3) (2).
A
(73 mg, 0.26 mmol) and HCtCCO2CH3 (16 µL, 0.26 mmol).
The resulting solution was stirred for 45 min at room tem-
perature and then filtered through Kieselguhr. The filtrate
was concentrated to ca. 0.1 mL in vacuo, and addition of
methanol led to precipitation of an orange solid. The solvent
was decanted, and the solid was washed twice with methanol
and then dried in vacuo; yield 84 mg (42%). (b) A solution of
7 (125 mg, 0.23 mmol) in toluene (15 mL) was treated with
PCy3 (62 mg, 0.22 mmol). After the mixture was stirred for
45 min at room temperature, the solution was filtered through
Kieselguhr. The filtrate was concentrated to ca. 0.1 mL in
vacuo, and addition of methanol led to precipitation of an
orange solid. The solvent was decanted, and the solid was
washed twice with methanol and then dried in vacuo: yield
60 mg (34%). Anal. Calcd for C41H73O2P2Rh: C, 64.45; H,
9.64. Found: C, 64.89; H, 10.06. IR (Nujol, cm-1): ν(acac)
1593, 1528. 1H NMR (300 MHz, C6D6, 20 °C, δ): 5.04 (s, 1 H,
CH of acac); 2.20-1.18 (m, 66 H, C6H11); 1.81 (s, 6 H, CH3 of
acac). 31P{1H} NMR (121.45 MHz, C6D6): δ 49.9 (J Rh-P ) 191
Hz).
P r ep a r a tion of Rh (a ca c)(η2-HCtCCO2CH3)(P Cy3) (7).
The complex was prepared using the procedure described for
4, starting from 2 (111 mg, 0.26 mmol) and HCtCCO2CH3 (16
µL, 0.26 mmol). Complex 7 was isolated as a yellow solid:
yield 99 mg (68%). Anal. Calcd for C27H44O4PRh: C, 57.24;
H, 7.83. Found: C, 56.87; H, 8.31. IR (Nujol, cm-1): ν(CtC)
1810; ν(CdO) 1685; ν(acac) 1582, 1514. 1H NMR (300 MHz,
C7D8, 20 °C, δ): 5.63 (d, J Rh-H ) 3 Hz, tCH); 5.21 (s, 1 H, CH
of acac); 3.52 (s, 3 H, CO2CH3); 1.94-1.10 (m, 33 H, C6H11);
1.80 (s, 6 H, CH3 of acac). 1H NMR (300 MHz, C7D8, -50 °C,
δ): 1.88 and 1.75 (both s, 6 H, CH3 of acac). 13C{1H} NMR
(75.45 MHz, C7D8, 20 °C, δ): 188.5 and 182.8 (both br, CO of
acac); 158.8 (s, CO2CH3); 99.7 (s, CH of acac); 93.8 (dd, J Rh-C
) 17 Hz, J P-C ) 5 Hz, one C of CtC); 76.0 (dd, J Rh-C ) 19 Hz,
J P-C ) 5 Hz, one C of CtC); 51.5 (s, CO2CH3); 32.35 (d, J P-C
) 23 Hz, PCHCH2); 29.9 and 29.6 (both s, CH2); 28.65 (d, J P-C
) 11 Hz, PCHCH2); 27.15 (s, CH3 of acac); 26.9 (s, CH2). 13C-
{1H} NMR (75.45 MHz, C7D8, -60 °C, δ): 188.5 and 182.8
(both s, CO of acac); 95.5 (br, one of CtC); 76.9 (br, one of
CtC); 27.9 (s, CH3 of acac); 26.9 (d, J P-C ) 5 Hz, CH3 of acac).
31P{1H} NMR (121.45 MHz, C7D8): δ 50.0 (d, J Rh-P ) 172 Hz).
solution of 1 (130 mg, 0.31 mmol) in toluene (10 mL) was
treated with PCy3 (86 mg, 0.31 mmol). The resulting solution
was stirred for 15 min at room temperature and filtered
through Kieselguhr. <ssen>The filtrate was concentrated to
ca. 0.1 mL in vacuo; addition of methanol led to the precipita-
tion of a yellow solid. The solvent was decanted, and the
residue was washed twice with methanol and then dried in
vacuo. Compound 2 was isolated as a yellow solid: yield 173
mg (95%). Anal. Calcd for C31H54O2PRh: C, 62.83; H, 9.18.
Found: C, 62.99; H, 9.27. IR (Nujol, cm-1): ν(acac) 1575, 1500.
1H NMR (300 MHz, C6D6, 20 °C, δ): 5.20 (s, 1 H, CH of acac);
3.13 (br, 2 H, HCdCH); 2.60-2.42 (m, 4 H, CHCH2); 2.02 (m,
4 H, CH2); 2.2-1.2 (m, 37 H, C6H11 and CH2); 1.91 and 1.61
(both s, 6 H, CH3 of acac). 31P{1H} NMR (121.45 MHz, C6D6):
δ 47.2 (d, J Rh-P ) 183 Hz).
P r ep a r a tion of Rh (a ca c)(CO)(P Cy3) (3). A stream of CO
was passed through a solution of 2 (123 mg, 0.21 mmol) in
toluene (10 mL) for 15 min. The resulting solution was filtered
through Kieselguhr, and the filtrate was concentrated to ca.
0.1 mL in vacuo; addition of hexane led to the precipitation of
a yellow solid. The solvent was decanted, and the solid was
washed twice with hexane and then dried in vacuo: yield 82
mg (77%). Anal. Calcd for C24H40O3PRh: C, 56.47; H, 7.90.
Found: C, 56.36; H, 7.82. IR (Nujol, cm-1): ν(CO) 1945; ν-
(acac) 1583, 1518. 1H NMR (300 MHz, C6D6, 20 °C, δ): 5.32
(s, 1 H, CH of acac); 2.00-1.11 (m, 33 H, C6H11); 1.78 and 1.66
(both s, 6 H, CH3 of acac).31P{1H} NMR (121.45 MHz, C6D6):
δ 59.6 (J Rh-P ) 168 Hz).
P r epar ation of Rh (acac)(η2-CH3O2CCtCCO2CH3)(P Cy3)
(4). A solution of 2 (109 mg, 0.18 mmol) in hexane (15 mL)
was treated with CH3O2CCtCCO2CH3 (23 µL, 0.18 mmol)
whereupon the yellow solution rapidly became orange. After
stirring of the solution for 30 min at room temperature, an
orange solid was formed. The solvent was decanted, and the
solid was washed twice with hexane and dried in vacuo: yield
101 mg (89%). Anal. Calcd for C29H46O6PRh: C, 55.77; H,
7.42. Found: C, 55.48; H, 7.45. IR (Nujol, cm-1): ν(CtC)
1890; ν(CdO) 1710, 1690, ν(acac) 1590, 1520. 1H NMR (300
MHz, C7D8, 20 °C, δ): 5.41 (s, 1 H, CH of acac); 3.79 (s, 6 H,
CO2CH3); 2.19-1.20 (m, 33 H, C6H11); 1.86 (s, 6 H, CH3 of acac).
1H NMR (300 MHz, C7D8, -50 °C, δ): 1.91 and 1.80 (both s, 6
H, CH3 of acac). 13C{1H} NMR (75.45 MHz, C7D8, 20 °C, δ):
158.8 (s, CO2CH3); 99.8 (s, CH of acac); 88.25 (dd, J Rh-C ) 19
Hz, J P-C ) 6 Hz, CtC); 52.4 (s, CO2CH3); 32.15 (d, J P-C ) 23
Hz, PCHCH2); 29.2 (s, CH2); 27.6 (d, J P-C ) 11 Hz, PCHCH2);
26.4 (s, CH2). 13C{1H} NMR (75.45 MHz, C7D8, -50 °C, δ):
188.9 and 183.1 (both s, CO of acac); 88.55 (br CtC); 28.35 (d,
J P-C ) 6 Hz, CH3 of acac); 26.65 (s, CH3 of acac). 31P{1H} NMR
(121.45 MHz, C7D8): δ 48.8 (d, J Rh-P ) 167 Hz).
P r ep a r a tion of Rh (a ca c)H2(P Cy3)2 (8). A solution of 1
(105 mg, 0.23 mmol) in toluene (10 mL) was treated with PCy3
(129 mg, 0.46 mmol), while a slow stream of H2 was passed
through the solution for 30 min at room temperature. The
resulting solution was filtered through Kieselguhr, and the
filtrate was concentrated to ca. 0.1 mL in vacuo; addition of
hexane led to the precipitation of a white solid. The solvent
was decanted, and the solid was washed twice with hexane
and dried in vacuo: yield 118 mg (67%). Anal. Calcd for
P r ep a r a tion of Rh (a ca c)(η2-P h CtCP h )(P Cy3) (5). The
complex was prepared using the procedure described for 4,
starting from 2 (118 mg, 0.20 mmol) and PhCtCPh (36 mg,
0.20 mmol). Complex 5 was isolated as a yellow solid: yield
114 mg (86%). Anal. Calcd for C37H50O2PRh: C, 67.26; H,
7.63. Found: C, 66.96; H, 8.07. IR (Nujol, cm-1): ν(CtC)
1910; ν(acac) 1575, 1510. 1H NMR (300 MHz, CDCl3, 20 °C,
δ): 8.05-7.23 (m, 10 H, Ph); 5.40 (s, 1 H, CH of acac); 1.94-
1.02 (m, 33 H, C6H11); 1.94 (s, 6 H, CH3 of acac). 1H NMR
(300 MHz, CDCl3, -50 °C, δ): 2.01 and 1.86 (both s, 6 H, CH3
of acac). 13C{1H} NMR (75.45 MHz, CDCl3, 20 °C, δ): 187.7
and 183.4 (both br, CO of acac); 131.3, 130.6, 130.2, 128.2,
C
41H75O2P2Rh: C, 64.38; H, 9.88. Found: C, 64.35; H, 10.64.
IR (Nujol, cm-1): ν(Rh-H) 2120, 2085; ν(acac) 1600, 1510. 1H
NMR (300 MHz, C6D6, 20 °C, δ): 5.27 (s, 1 H, CH of acac);
2.21-1.26 (m, 66 H, C6H11); 1.93 (s, 6 H, CH3 of acac); -22.18
(dt, 2 H, J Rh-H ) 20 Hz, J P-H ) 16 Hz, Rh-H). 31P{1H} NMR
(80 MHz, C6D6): δ 15.8 (d, J Rh-P ) 117 Hz).
P r ep a r a tion of Rh (a ca c)H(CtCP h )(P Cy3)2 (9). A solu-
tion of 2 (83 mg, 0.14 mmol) in toluene (10 mL) was treated
with PCy3 (40 mg, 0.14 mmol) and PhCtCH (16 µL, 0.14
mmol). The resulting reaction mixture was stirred for 6 h at
room temperature and then filtered through Kieselguhr. The
filtrate was concentrated to ca. 0.1 mL in vacuo, and the
addition of methanol led to the precipitation of a white solid.
The solvent was decanted, and the solid was washed twice with
methanol and dried in vacuo: yield 57 mg (47%). Anal. Calcd
for C49H79O2P2Rh: C, 68.04; H, 9.21. Found: C, 67.75; H, 9.66.
IR (Nujol, cm-1): ν(Rh-H) 2155; ν(CtC) 2118; ν(acac) 1600,
1515. 1H NMR (300 MHz, CDCl3, 20 °C, δ): 9.90-7.45 (m, 5
H, Ph); 5.35 (s, 1 H, CH of acac); 2.40-1.20 (m, 66 H, C6H11);
2.08 and 1.86 (both s, 6 H, CH3 of acac); -18.79 (dt, 1 H, J Rh-H
) 19 Hz, J P-H ) 12 Hz, Rh-H). 13C{1H} NMR (75.45 MHz,
CDCl3, 20 °C, δ): 188.3 and 184.4 (both s, CO of acac); 130.7,
127.4, 125.9 (all s, Ph); 99.2 (s, CH of acac); 86.2 (dd, J Rh-C
)
17 Hz, J P-C ) 4 Hz, CtC); 32.6 (d, J P-C ) 23 Hz, PCHCH2);
29.6 (s, CH2); 27.8 (d, J P-C ) 10 Hz, PCHCH2); 26.8 (s, CH2).
13C{1H} NMR (75.45 MHz, CDCl3, -50 °C, δ): 86.2 (br, CtC);
28.15 (d, J P-C ) 4 Hz, CH3 of acac); 26.95 (s, CH3 of acac).
31P{1H} NMR (121.45 MHz, CDCl3): δ 49.6 (d, J Rh-P ) 179
Hz).
P r ep a r a tion of Rh (a ca c)(P Cy3)2 (6). This complex can
be prepared by two different procedures. (a) A solution of 2
(154 mg, 0.26 mmol) in toluene (10 mL) was treated with PCy3
+
+

Reactions of a Monoolefin Complex
Organometallics, Vol. 15, No. 15, 1996 3443
Ta ble 3. Cr ysta l Da ta a n d Da ta Collection a n d Refin em en t for Rh (a ca c)(P Cy3)2 (6) a n d
[Rh (a ca c){(E)-CHdCHCy)(P Cy3)2]BF 4 (12)
6
12
Crystal Data
C41H73O2P2Rh
762.88
formula
mol wt
C49H79BF4O2P2Rh
951.84
color and habit
cryst size, mm
cryst syst
space group
a, Å
orange, irregular prism
0.41 × 0.32 × 0.31
triclinic
P1h (No. 2)
10.400(3)
yellow, irregular prism
0.25 × 0.38 × 0.38
monoclinic
P21/n (No. 14)
12.463(4)
b, Å
11.593(3)
20.861(4)
c, Å
18.708(6)
21.025(7)
R, deg
83.55(2)
85.08(2)
65.52(2)
2037(1), 2
1.24
173
â, deg
101.03(2)
γ, deg
V, Å3; Z
D(calcd), g cm-3
temp (K)
5365, 4
1.18
293
Data Collection and Refinement
diffractometer
λ(Mo KR) radiation, Å;
technique
Siemens-STOE AED-2
0.710 73
bisecting geometry
graphite oriented
0.53
ω/2θ
3 e 2θ e 50
7569
Enraf-Nonius CAD-4
0.709 30
κ geometry
graphite, Zr filter (factor 15.41)
0.42
ω/θ
2 e 2θ e 48
8383
monochomator
µ, mm-1
scan type
2θ range, deg
no. of data collcd
no. of unique data
no. of obsd data
no. of params refined
R1(6, 12)a
7146
7505
5390 (Fo > 4.0σ(Fo))
417
0.0462
0.1256
5023 (Fo > 3.0σ(Fo))
539
0.060
0.093
wR2(6),b Rw(12)c
a
b
2
R1(F) ) ∑||Fo| - |Fc||/∑|Fo|. wR2(F2, all data) ) {∑[w(Fo - Fc2)2]/∑[w(Fo2)2]}1/2
.
c Rw ) ∑(w1/2|[Fo - Fc]|)/(∑w1/2Fo).
.
130.6, 167.7, 123.4 (all s, Ph); 106.25 (d, J Rh-C ) 10 Hz,
CtCPh); 103.85 (dt, J Rh-C ) 48 Hz, J P-C ) 16 Hz, CtCPh);
99.55 (s, CH of acac); 33.8 and 33.7 (both d, J P-C ) 20 Hz,
PCHCH2); 29.9 and 29.5 (both s, CH2); 28.65 and 28.4 (both d,
J P-C ) 8 Hz, PCHCH2); 27.4 and 27.3 (s, CH2); 23.75 (s, CH3
(15 mL) was treated with HBF4 OEt2 (16 µL, 0.12 mmol),
causing an immediate color change to bright yellow. After the
mixture was stirred for 30 min at room temperature, a yellow
precipitate formed. The solvent was decanted, and the solid
was washed twice with diethyl ether and then dried in vacuo;
yield 93 mg (81%). Anal. Calcd for C49H86BF4O2P2Rh: C,
61.38; H, 9.04. Found: C, 60.87; H, 9.34. IR (Nujol, cm-1):
ν(acac) 1570, 1530. 1H NMR (300 MHz, CDCl3, 20 °C, δ): 6.50
(dt, 1 H, J H-H ) 10 Hz, J P-H ) 9Hz, RhCHdCHCy); 5.90 (s, 1
H, CH of acac); 4.25 (dd, 1 H, J H-H ) 10 Hz, J Rh-H ) 8 Hz,
RhCHdCHCy); 2.59-1.00 (m, 77 H, C6H11); 2.11 (s, 6 H, CH3
of acac). 13C{1H} NMR (75.45 MHz, CDCl3, 20 °C, δ): 185.2
(s, CO of acac); 135.6 (s, RhCHdCHCy); 111.6 (dt, J Rh-C ) 35
Hz, J P-C ) 9 Hz, RhCHdCHCy); 99.8 (s, CH of acac); 35.6 (d,
J P-C ) 22 Hz, PCHCH2); 32.1 (s, Cy); 29.95 and 28.7 (both s,
CH2); 27.0 and 26.8 (both d, J P-C ) 10 Hz, PCHCH2); 26.2 (s,
CH2); 25.6 (s, CH3 of acac); 25.4, 25.2, 24.9 (all s, CH2). 31P-
{1H} NMR (80 MHz, CDCl3): δ 28.7 (d, J Rh-P ) 132 Hz).
of acac). 31P{1H} NMR (80 MHz, C6D6): δ 38.0 (d, J Rh-P
)
103 Hz).
P r ep a r a t ion of R h (a ca c)H(CtCCy)(P Cy3)2 (10). The
complex was prepared using the procedure described for 9,
starting from 2 (166 mg, 0.28 mmol), PCy3 (78 mg, 0.28 mmol),
and CyCtCH (36 µL, 0.28 mmol). Complex 10 was isolated
as a pale yellow solid: yield 115 mg (47%). Anal. Calcd for
C
49H85O2P2Rh: C, 67.57; H, 9.84. Found: C, 67.75; H, 10.03.
IR (Nujol, cm-1): ν(Rh-H) 2140; ν(CtC) 2115; ν(acac) 1600,
1515. 1H NMR (300 MHz, CDCl3, 20 °C, δ): 5.35 (s, 1 H, CH
of acac); 2.40-1.20 (m, 77 H, C6H11); 2.04 and 1.72 (both s, 6
H, CH3 of acac); -19.33 (dt, 1 H, J Rh-H ) 18 Hz, J P-H ) 13
Hz, Rh-H). 13C{1H} NMR (75.45 MHz, CDCl3, 20 °C, δ):
187.9 and 184.1 (both s, CO of acac); 107.45 (d, J Rh-C ) 10 Hz,
CtCCy); 101.85 (dt, J Rh-C ) 40 Hz, J P-C ) 18 Hz, CtCCy);
99.3 (s, CH of acac); 35.0 (s, CH2); 33.5 and 33.4 (both d, J P-C
) 23 Hz, PCHCH2); 29.65 and 29.6 (both s, CH2); 26.9 (s, CH2);
26.5 (s, CH3 of acac); 26.0 (s, CH2). 31P{1H} NMR (80 MHz,
C6D6): δ 37.1 (d, J Rh-P ) 104 Hz).
P r ep a r a tion of [Rh (a ca c)(CHdCDCy)(P Cy3)2]BF 4 (12-
d 1). To prepare a solution of DBF4, 1 mL of D2O was added
dropwise to an equal volume of HBF4 OEt2 until effervescence
ceased. Addition of the stoichiometric amount of this solution
to an ether slurry of 11 proceeded as described above for the
preparation of 12. 1H NMR (300 MHz, CDCl3, 20 °C, δ): 6.56
(t, 1 H, J P-H ) 10 Hz, RhCHdCDCy); 5.90 (s, 1 H, CH of acac);
2.59-1.00 (m, 77 H, C6H11); 2.11 (s, 6 H, CH3 of acac). 2H NMR
(46.07 MHz, CH2Cl2, 20 °C, δ): 4.33 (s, RhCHdCDCy). 31P-
{1H} NMR (80 MHz, CDCl3): δ 28.9 (d, J Rh-P ) 132 Hz).
P r ep a r a tion of [Rh (a ca c)(CHdCH2)(P Cy3)2]BF 4 (13).
The complex was prepared using the procedure described for
12 starting from 11 (112 mg, 0.13 mmol) and HBF4 OEt2 (18
µL, 0.13 mmol). Compound 13 was isolated as a yellow solid:
yield: 87 mg (76%). Anal. Calcd for C43H76BF4O2P2Rh: C,
58.91; H, 8.74. Found: C, 58.30; H, 9.03. IR (Nujol, cm-1):
ν(acac) 1573, 1530. 1H NMR (300 MHz, CDCl3, 20 °C, δ): 7.31
(m, RhCHdCH2); 5.91 (s, 1 H, CH of acac); 4.38 (br, 1H, one
H of RhCHdCH2 cis to Rh); 4.22 (dd, 1 H, J H-H ) 12 Hz, J Rh-H
) 5 Hz, one H of RhCHdCH2 trans to Rh); 2.59-1.00 (m, 77
.
P r epar ation of Rh (acac)H(CtCSiMe3)(P Cy3)2 (11). The
complex was prepared using the procedure described for 9,
starting from 2 (142 mg, 0.24 mmol), PCy3 (67 mg, 0.24 mmol),
and Me3SiCtCH (34 µL, 0.24 mmol). Complex 11 was isolated
as a white solid: yield 95 mg (46%). Anal. Calcd for
C
46H83O2P2RhSi: C, 64.16; H, 9.72. Found: C, 64.52: H;
10.68. IR (Nujol, cm-1): ν(Rh-H) 2146; ν(CtC) 2042; ν(acac)
1587, 1514. 1H NMR (300 MHz, CDCl3, 20 °C, δ): 5.10 (s, 1
H, CH of acac); 2.19-1.18 (m, 66 H, C6H11); 1.84 and 1.69 (both
s, 6 H, CH3 of acac); 0.20 (s, 9 H, CH3Si); -19.19 (dt, 1 H,
J Rh-H ) 18 Hz, J P-H ) 13 Hz, Rh-H). 31P{1H} NMR (80 MHz,
CDCl3): δ 35.6 (d, J Rh-P ) 102 Hz).
.
P r ep a r a tion of [Rh (a ca c){(E)-CHdCHCy}(P Cy3)2]BF 4
(12). A suspension of 10 (100 mg, 0.12 mmol) in diethyl ether
+
+

3444 Organometallics, Vol. 15, No. 15, 1996
Esteruelas et al.
H, C6H11); 2.11 (s, 6 H, CH3 of acac). 13C{1H} NMR (75.45
MHz, CDCl3, 20 °C, δ): 186.2 (s, CO of acac); 127.3 (dt, J Rh-C
) 37 Hz, J P-C ) 9 Hz, RhCHdCH2); 117.6 (s, RhCHdCH2);
100.7 (s, CH of acac); 36.3 (d, J P-C ) 20 Hz, PCHCH2); 30.75
and 29.65 (both s, CH2); 27.8 (d, J P-C ) 10 Hz, PCHCH2); 26.25
(s, CH3 of acac); 25.9 (s, CH2). 31P{1H} NMR (80 MHz,
CDCl3): δ 28.7 (d, J Rh-P ) 130 Hz).
X-r a y Str u ctu r e An a lysis of Rh (a ca c)(P Cy3)2 (6). Crys-
tals suitable for an X-ray diffraction experiment were obtained
by slow diffusion of hexane into a concentrated solution of 6
in CH2Cl2. A summary of crystal data, intensity collection
procedure, and refinement data is reported in Table 3. The
crystal studied was glued on a glass fiber and mounted on a
Siemens AED-2 diffractometer. Cell constants were obtained
from the least-squares fit of the setting angles of 65 reflections
in the range 20 e 2θ e 30°. The recorded reflections were
corrected for Lorentz and polarization effects. Reflections were
also corrected for absorption by an empirical method (ψ-scan
method).24
The structure was solved by Patterson (Rh atom) and
conventional Fourier techniques. Refinement was carried out
by full-matrix least-squares methods with initial isotropic
thermal parameters. Hydrogen atoms were calculated accord-
ing to the ideal geometry (distance C-H ) 0.96 Å) and
included in the refinement riding on carbon atoms with a
commom isotropic thermal parameter. Anisotropic thermal
parameters were used in the last cycles of refinement for all
non-hydrogen atoms. All calculations were performed using
SHELXTL-PLUS25 and SHELX-93.26
X-r ay Str u ctu r e An alysis of [Rh (acac){(E)-CHdCHCy}-
(P Cy3)2]BF 4 (12). Crystals suitable for an X-ray diffraction
experiment were obtained by slow diffusion of diethyl ether
into a concentrated solution of 12 in CH2Cl2. A summary of
crystal data, intensity collection procedure, and refinement
data is reported in Table 3. The crystal studied was glued on
a glass fiber and mounted on a Enraf-Nonius CAD-4 diffrac-
tometer. Cell constants were obtained from the least-squares
fit of the setting angles of 23 reflections in the range 20 e 2θ
e 26°. Intensity data were corrected for Lorentz and Polariza-
tion effects, and a semiempirical absorption correction (ψ-scan
method) was applied.24 The structure was solved by direct
methods (SHELXS-86).27 Atomic coordinates and anisotropic
thermal parameters of the non-hydrogen atoms were refined
by full-matrix least-squares methods (unit weights, Enraf-
Nonius SDP28). The hydrogen atoms were calculated according
to the ideal geometry (distance C-H ) 0.95 Å) and used only
in structure factor calculations. The BF4 group was found to
be disordered over three sites; with equal occupancies the
positions were refined independently with isotropic tempera-
ture factors.
Ack n ow led gm en t. We thank the DGICYT (Projet
PB 92-0092, Programa de Promocio´n General del Cono-
cimiento) and European Community (Network ERB-
CHRXCT 930147; Project: Selective Processes and
Catalysis Involving Small Molecules) for financial sup-
port. E.O. thanks the DGA (Diputacio´n General de
Arago´n) for a grant. L.R. thanks the Spanish Govern-
ment for a grant (Programa de Formacio´n Cient´ıfica
para Iberoame´rica). P.S. and H.W. acknowledge sup-
port by the Deutsche Forschungsgemeinschaft (Grant
SFB 347).
Su p p or tin g In for m a tion Ava ila ble: Tables of anisotro-
pic thermal parameters, complete atomic coordinates and
thermal parameters, experimental details of the X-ray study,
bond distances and angles, selected least-squares planes, and
interatomic distances (31 pages). Ordering information is
given on any current masthead page.
OM9601458
(24) North, A. C. T.; Phillips, D. C.; Mathews, F. S. Acta Crystallogr.
1986, A24, 351.
(25) Sheldrick, G. SHELXTL-PLUS; Siemens Analytical X-ray Inst.
Inc., Madison WI, 1990.
(26) Sheldrick, G. SHELXL-93 Program for Crystal Structure
Refinement, Institut fu¨r Anorganische Chemie der Universita¨t, Go¨t-
tingen, Germany, 1990.
(27) Sheldrick, G. SHELXS-86 Program for Crystal Structure Solu-
tion, Institut fu¨r Anorganische Chemie der Universita¨t, Go¨ttingen,
Germany, 1986.
(28) Frentz, B. A. The Enraf-Nonius CAD-4 SDP, a real system for
concurrent X-Ray data collection and structure determination. In
Computing in Crystallography; Delft University Press: Delft, Holland,
1978; pp 64-71.
+
+